How to Write a Side Character

Without a side character, your story is just a blob with a vague purpose and meaning. Without connections, your character isn't a person; they're just a thing. Connections are what make you you. Would you be the same person if you didn't know your mom, your dad, your siblings, your friends? What really "defines" you is a question that's too complex for this article to answer.

First, what makes the character themself? What is their cornerstone? Without this, there isn't anything to build on. The most common examples of this are the lone wolf, the hero, the healer, the comedian, and the mentor. Obviously, there are more types than this, but these are the main archetypes. 

Next, what makes the side character different from these archetypes? If everyone used these in every story, each story would be the same (and some argue they are). You have to decide what builds them up from their cornerstone. This is their walls and roof. Without it, you just have a slab of concrete, not the beginnings of a house.

After this, you populate them with fine details. Their habits, their hobbies. How does this shape them and the ones around them? How do they affect your plot and your message? Do they leave a lasting legacy on the world after they're gone? Who are they really? 

Finally, how do they affect the main character? Are they a lover, a friend, a rival? Do they even know each other? What is their message? How do they help the story you want to tell? Are they avatars of a feeling, a god, a motivation? What is their purpose? 

This is the framework of a side character. The great thing about writing them is that you don't need to make them complex. You don't need to write their thoughts. Of course, you still want to make them unique for it to be a good story. The way I see them is as a lens reflecting the light of the main character; they're more like a magnifying glass examining what is already there with them, sometimes for better and sometimes for worse. Their existence is to make your MC react and do different things.

Obviously, you could examine them with their own chapters by giving them personal points of view or, better yet, find an excuse to meld their mind with the main character for a paragraph or two once or twice a book. You also can't have your side characters do the same thing every time. They have to do their own thing. Sometimes, let them off the leash of the main character and have them do their own thing. Finally, you have to be able to let go of a side, let them die, let them move on, let them leave.

Sources “Craft Intriguing Secondary Characters in Exactly 7 Steps.” Www.dabblewriter.com, www.dabblewriter.com/articles/secondary-characters.